Antioxidant and antimicrobial properties of hibiscus Rosa-Sinensis

Leong, Soo Fong (2005) Antioxidant and antimicrobial properties of hibiscus Rosa-Sinensis. Universiti Malaysia Sabah. (Unpublished)

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Abstract

The objectives of this study were to determine the antioxidant activities and antimicrobial activities of the flavonoid glycoside, flavonoid aglycone, flavonol and anthocyanin extracts of 'Bung a Raya' (Hibisucs rosa-sinensis) leaves and petals against Listeria monocytogenes L55 and Salmonella typhimurium S1000. The antioxidant activities of Hibiscus extracts were evaluated by the 2, 2' -diphenyl -l-picrylhydrazyl (DPPH) radical scavenging and p-carotene bleaching methods. Anthocyanin extracts of petals had the highest total phenolic contents (67.80:t 0.80mg/g extract in gallic acid equivalent) among the Hibiscus extracts tested. The anthocyanin and flavonoid aglycone extracts showed a good scavenging ability in DPPH radical scavenging and exhibited an excellent total antioxidant activity in β-carotene-linoleic acid assay. Both tester bacteria susceptibility profiles were carried out using various antibiotics to show that both tester bacteria which used for antimicrobial test were in inherent or have not occured any mutation. The result indicated that L. monocytogenes was sensitive to all antibiotics tested and only resistance to Oxacilin (1µg). Meanwhile S. typhimurium was resistant to Penicillin G (10µg) and Oxacillin (1µg) but susceptible to other antibiotics. Disc diffusion method was used to screen the antimicrobial activity of each extract on both tester bacteria. Flavonoid aglycone extracted from the leaves seems to be the most active extracts with largest inhibition zone towards L. monocytogenes (19.75± 0.50 mm) and S. typhimurium (18.34 ±0.52 mm). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extracts were investigated by using the broth dilution method. MIC and MBC value of flavonoid aglycone was the lowest followed by anthocyanin, flavonoid glycoside and flavonol on both tested organisms. The flavonoid aglycone inhibited L. monocytogenes and S. typhimurium with MIC values of 21.50 mg/ml and 23.45 mg/ml respectively. Meanwhile the MBC value of this extract on the same bacteria was determined as 22.48 mg/ml and 25.41 mg/ml. Flavonol was found less effective in controlling L. monocytogenes and S. typhimurium with higher MIC (82.02 mg/ml and 132.82 mg/ml). The decimal reduction times required by L. monocytogenes population in broth system containing flavonoid aglycone and anthocyanin were 10.38 hours and 10.19 hours respectively according to their MIC values. As a conclusion, flavonoid aglycone and anthocyanin extracts showed a good antimicrobial activity among the Hibiscus extracts and therefore both flavonoid aglycone and anthocyanin have the potential for further studies of their effectiveness in the development of a natural preservative.

Item Type: Academic Exercise
Uncontrolled Keywords: antioxidant, antimicrobial, flavonoid glycoside, flavonoid aglycone, flavonol, Hibisucs rosa-sinensis, extract, natural preservative
Subjects: Q Science > QR Microbiology
Divisions: SCHOOL > School of Food Science and Nutrition
Depositing User: MDM SITI AZIZAH IDRIS
Date Deposited: 25 Sep 2013 03:33
Last Modified: 17 Oct 2017 03:11
URI: http://eprints.ums.edu.my/id/eprint/7061

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